1. Field of the Invention
This invention relates, generally, to non-destructive inspection and inspection equipment, and more specifically, to provide automatic and/or continuous non-destructive inspection and evaluation to material under inspection, including evaluators and predictors of detected imperfections and useful material life.
2. Description of the Prior Art
As is known in the art, materials are selected for use based on criteria including minimum strength requirements, useable life, and anticipated normal wear. Safety factors are typically factored into design considerations to supplement material selection in order to aid in reducing the risk of failures including catastrophic failures. Such failures may occur when the required application strengths exceed the actual material strength. During its useful life, material deteriorates and/or is weakened by external events such as mechanical and/or chemical actions arising from the type of application, repeated usage, hurricanes, earthquakes, storage, transportation, and the like; thus, raising safety, operational, functionality, and serviceability issues requiring the determination of the material remaining strength for the type of application.
The non-destructive-inspection industry (herein after referred to as “NDI”) has utilized a variety of techniques and devices with the majority based on the well known and well documented techniques of audible, color, dimensional, dye penetrant, eddy-current, emat, magnetic flux leakage, laser, magnetic particle, radiation, such as x-ray and gamma ray, sound, ultrasonic and visual techniques. These techniques have been utilized alone or in combination with each other to address the specifics of the Material-Under-Inspection (herein after referred to as “MUI”). A list of typical MUI includes, but is not limited to, aircraft, bridges, cranes, drilling rigs, frames, chemical plant components, engine components, risers and riser components, oil country tubular goods (herein after referred to as “OCTG” or “tubular goods”), pipelines, power plant components, rails, refineries, rolling stoke, sea going vessels, service rigs, structures, vessels, workover rigs, other components of the above, combinations of the above, and similar items.
Typical NDI devices deploy a single sensor per material area and are therefore classified as one-dimensional (herein after referred to as “1D-NDI”). 1D-NDI comingles all MUI signals into one sensor signal, thus it does not permit for the solution of a system of equations that describes MUI and significantly limits the 1D-NDI dynamic range. Because of the signal comingling and the limited dynamic range, 1D-NDI cannot detect many of the dangerous imperfections early on, such as fatigue, and has a limited operational range for pipe size, configuration, wall thickness, types of imperfections, inspection speed, sampling rate and similar items while it still relies on the manual intervention of a verification-crew to locate and identify the source of the 1D-NDI signal. Instead of an affirmative verification that MUI exceeds the minimum strength requirements for the application, NDI is carried out with the aid of a manual verification crew, to determine that the few imperfections within the NDI detection capabilities are not present. Thus, the NDI limitations govern the inspection process and outcome, not MUI needs, the application needs or the safety needs.
In addition, NDI dictates termination of MUI utilization altogether in order to accommodate the inspection process, which, is typically carried out by shipping MUI to an inspection facility (illustrated in FIG. 4), regardless if it needs inspection or maintenance, because NDI cannot determine the need onsite and the NDI data cannot be used to calculate a remaining strength or the next inspection interval. Furthermore, NDI imposes, at minimum, cleaning of MUI, removal of paint or coating and other similar restrictions; thus, NDI is, at minimum, an intrusive process. When MUI paint or coating is removed, NDI is a destructive process. NDI would be non-destructive if it inspects MUI without removing the paint or coating. And non-intrusive if inspects MUI where-is as-is. Again, NDI cannot detect imperfections early on. Instead, NDI focuses on end-of-life imperfections where deterioration is accelerated significantly and which are detectable by a manual verification crew.
For complex OCTG, such as a marine drilling riser (herein after referred to as “Riser”), illustrated as item 71 in FIG. 3, this process also requires the removal of buoyancy; cleaning; disassembly; removal of paint or coating (illustrated in FIG. 4); performing a very limited 1D-NDI comprising of a few spot-checks that typically results in less than 1% inspection coverage (illustrated in FIG. 5, 6); re-painting or re-coating; re-assembly; installation of the buoyancy and shipping back to the rig with about 99% of Riser condition still unknown. The cost of inspection is therefore increased by the transportation and handling cost along with the material downtime. In addition, assembly errors and omissions along with the shipping and handling, especially after the inspection, may induce damage to Riser that could result in an unanticipated early catastrophic failure.
Because of its implementation and the intrusion NDI limitations impose, typical inspections have been expensive and thus are performed at rare intervals or not performed at all. Risers, for example, are shipped to shore for inspection on a five year cycle, with 20% of Risers inspected per year, in a process that provides insignificant inspection coverage but may be harmful, especially for Risers that do not need any maintenance. In addition, NDI costs can be as high as 30% of the OCTG replacement cost.